Catecholamines and prostaglandins are thought to have important roles in the control of reproduction. We propose to study the hypothesis that an Alpha-adrenergic circuit in brain is critical for the maintenance of sexual receptivity in the guinea pig and that the termination of estrus which follows copulation may be due to a decline in activity in this circuit. We will also test the possibility that this decline is mediated by prostaglandin, perhaps released from the female reproductive tract. Our techniques will include intracranial injection of prostaglandin and related drugs along with Alpha1 and Alpha2-adrenergic agents, and assays of prostaglandins, receptor binding, no repinephrine release and cAMP. We will also be interested in the application of these findings to other reproductive events in guinea pig, rat and monkey.